Patients with rubeosis iridis and neovascular glaucoma are being recruited. These with salvageable vision are invited to join this prospective, randomized study of whether cyclocryotherapy or cyclodiathermy is better for the treatment of this disease. Outcome will be judged by assessing preservation of visual function; adequate control of intraocular pressure, with or without medications; and control of discomfort. It is estimated that approximately 40 non-diabetic and 40 diabetic patients will be needed for this project.